Bed exit alarm of hospital bed mattress

ABSTRACT

A mattress system includes a mattress, a control unit spaced from the mattress, and a connector assembly that pneumatically and electrically interconnects the control unit with the mattress. The control unit has a main housing and a plurality of user interface modules that are selectively coupleable to the control unit and that are programmed differently to provide different modes of operation for the mattress system. A pressure sensor inside the mattress detects the presence or absence of a person on the mattress. The mattress system has a bed exit alarm system that, when armed, provides a bed exit alarm if the pressure sensor in the mattress detects that a patient has exited the mattress. The connector assembly includes a dual mode connector having both electrical and pneumatic couplers and a dual lumen hose assembly that extends from the dual mode connector to the mattress.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.11/559,529, filed Nov. 14, 2006, which issued as U.S. Pat. No. 7,849,545on Dec. 14, 2010 and which is hereby incorporated by reference herein.

BACKGROUND OF THE INVENTION

The present disclosure relates to hospital bed mattresses andparticularly, to control systems for hospital bed mattresses in whichportions of the control systems may control inflation of one or more airbladders included in the mattresses and portions of the control systemsmay control bed exit alarms. The present disclosure also relates to hoseassemblies that interconnect control units with associated mattresses.

Hospitals use a variety of different mattress types to support patientshaving different medical needs. Some patients benefit from beingsupported on alternating pressure mattresses or rotation therapymattress. Other patients may not need to be supported on these types ofmattresses having dynamic therapies, but rather, so-called static airmattresses that simply operate to provide a relatively low interfacepressure may be suitable for such patients. To address these variousmattress requirements, manufacturers may market a number of mattressproducts, each with its own particularized therapeutic function, or maymarket mattresses that have control units allowing users to program orselect different modes of operation. It can be expensive for hospitalsor other healthcare institutions to purchase a large number ofmattresses, each having its own dedicated therapeutic functionality.However, mattresses allowing user selectable functionality introduce thepossibility that users may inadvertently configure the mattress with thewrong type of therapy or operation among the plurality of the availabletherapies.

It is sometimes desirable for patients to remain in bed and, in suchsituations, hospitals are interested in having some type of bed exitalarm for these patients to provide an alarm or alarm signal indicatingthat the patient has exited, or is about to exit, the bed. Some bedframes have built-in bed exit alarm systems, oftentimes using the loadcells of a weigh scale system, to determine the presence or absence of apatient on the bed and triggering a bed exit alarm when a thresholdamount of weight is determined to have been removed from the bed. Theaddition of a weigh scale system to a bed frame adds cost and therefore,hospitals purchase many bed frames without the weigh scale system optionand consequently, therefore, without any bed exit alarm capability.Separate bed exit systems having strips or mats that are placed on topof a mattress and underneath a patient are known in the art, but suchstrips or mats may result in increased interface pressure on the patientand thus, may compromise the ability of the mattress to support thepatient with relatively low interface pressure.

SUMMARY OF THE INVENTION

The present invention comprises an apparatus or system having one ormore of the features recited in the appended claims and/or one or moreof the following features, which alone or in any combination maycomprise patentable subject matter:

A mattress system may comprise a mattress having at least one inflatablebladder and a control unit. The control unit may comprise a mainhousing, a source of pneumatic pressure carried by the main housing andoperable to inflate the at least one inflatable bladder, and a pluralityof user interface modules that are coupleable to the main housing. Eachuser interface module may be programmed to control inflation of the atleast one air bladder differently in at least one operational mode ofeach of the plurality of user interface modules.

The user interface modules may include an alternating pressure moduleand a continuous low pressure module. Additionally or alternatively, theuser interface modules may include a rotation therapy module. One ormore the user interface modules may be programmed to provide twodifferent types of therapies. Each of user interface modules may haveuser inputs that are used to change a mode of operation of theassociated user interface module. One or more of the user interfacemodules may be programmed to provide a maximum inflation mode in whichthe at least one inflatable bladder is inflated to a maximum thresholdpressure which renders the at least one air bladder suitably hard forpatient transfer. One or more of the user interface modules may includeat least one visual indicator that is operable to provide visualindication of the operational status of the mattress system.

The control unit may have a latch coupled to the main housing andmovable between a locked position in which a selected one of theplurality of user interface modules is locked to the main housing and anunlocked position in which the selected one of the plurality of userinterface modules is detachable from the main housing. The latch mayhave a hook and each of the user interface modules may have a post thatis captured by the hook when the associated user interface module islocked to the main housing by the latch. The main housing may have atleast one slot and each of the plurality of interface modules may haveat least one tab that is received in the slot provided in the mainhousing when the associated user interface module is coupled to thehousing.

Each of the user interface modules may comprise a main body. The postand the at least one tab of each of the plurality of user interfacemodules may be located on opposite ends of the associated user interfacemodules. The post and the at least one tab of each of the plurality ofuser interface modules may extend away from the associated main body inopposite directions.

The main housing of the control unit may have a recess into which eachof the user interface modules is insertable. The control unit mayinclude a first electrical connector coupled to the main housing. Eachof the user interface modules may include a second electrical connectorthat automatically mates with the first electrical connector uponinsertion of the user interface module into the recess of the mainhousing.

At least one of the plurality of user interface modules may have alockout switch that is usable to lockout at least one operational modeof the associated user interface module. The lockout switch may belocated adjacent a surface, such as a back surface, of the associateduser interface module that is inaccessible to a user when the associateduser interface module is coupled to the main housing. The lockout switchmay be used to lockout the maximum inflation mode of the associated userinterface module.

One or more of the plurality of user interface modules may includeinputs that are engageable to enable a bed exit alarm system of thecontrol unit. The bed exit alarm system may receive an input signal fromthe mattress indicative of a pressure sensed by a pressure sensorsituated in an interior region of the surface.

The source of pneumatic pressure of the control unit may comprise an aircompressor within a noise-dampening housing that is situated within aninterior region of the main housing. The noise-dampening housing mayhave an air chamber that serves as a pressure reservoir which stabilizesair flow to the at least one air bladder of the mattress.

The mattress may at least one valve located within an interior region ofthe mattress. The valve may be opened and closed to control pressure inthe at least one inflatable bladder in a manner dictated by theprogramming of the selected user interface module that is coupled to themain housing. The mattress may have at least one pressure sensorsituated within an interior region of the mattress and an output signalfrom the at least one pressure sensor may be communicated to theselected user interface module that is coupled to the main housing. Atleast one cardiopulmonary resuscitation (CPR) input may be coupled tothe mattress and may be movable mechanically to deflate the at least oneair bladder of the surface. Movement of the CPR input may result in aCPR signal being communicated to the selected user interface module thatis coupled to the main housing. The selected user interface module maydeactivate operation of the source of pneumatic pressure in response toreceiving the CPR signal.

The control unit may have circuitry that receives a signal from themattress which is indicative of a pressure sensed by a pressure sensorsituated within an interior region of the mattress. The circuitry mayuse the signal to establish at least one target pressure to which the atleast one inflatable bladder is controlled. The circuitry may also usethe signal to determine whether to activate a bed exit alarm. The bedexit alarm may comprise a flashing light that is carried by the controlunit. Alternatively or additionally, the bed exit alarm may comprise asound-producing device, such as a speaker or buzzer, carried by thecontrol unit.

The pressure sensor may comprise a bag filled with silicon oil. Themattress comprises an inflatable underlay having a space that receivesthe bag filled with silicon oil. The at least one inflatable bladder ofthe mattress may comprise at least one inflatable layer that overliesthe pressure sensor. The at least one inflatable layer may comprisefirst and second inflatable layers that overlie the pressure sensor. Thefirst inflatable layer may comprise a plurality of laterally extendingair bladders, at least two of which are inflatable to differentpressures. The second inflatable layer may extend approximately the fulllength of the mattress and may be inflatable to a single targetpressure.

The mattress may have one or more foam layers, blocks, pads, and/or oneor more other non-inflatable support elements in lieu of, or in additionto, the at least one inflatable bladder. Accordingly, the mattress mayhave no inflatable bladders at all. A pressure sensor comprising anenclosure containing a liquid, such as a bag filled with silicon oil,may be used as part of a bed exit alarm system in such a foam mattress.With regard to mattresses lacking any inflatable bladders, the controlunit may be omitted and the circuitry and sound-producing device of thebed exit alarm system may be included within, or coupled directly to,the mattress itself. In other embodiments, some or all of the circuitryand sound producing device of the bed exit alarm system may be situatedin a housing or module that is spaced from the mattress and that iscoupled to the pressure sensor via one or more electrical lines, or evenwirelessly for that matter.

The mattress may have at least one electrical component situated withinan interior region of the mattress, a first pneumatic port incommunication with the at least one inflatable bladder of the mattress,and a first electrical connector in communication with the at least oneelectrical component. The circuitry of the control unit may beprogrammed to control the manner in which the at least one inflatablebladder is inflated. The circuitry may also include a second electricalconnector and the control unit may include a second pneumatic port incommunication with the source of pneumatic pressure.

A connector assembly may be provided to pneumatically connect the firstpneumatic port with the second pneumatic port and to electricallyconnect the first electrical connector with the second electricalconnector. The connector assembly may include a pneumatic line, at leastone electrical line, and a dual mode plug configured to permitconnection of the pneumatic line with the second pneumatic connectorsubstantially simultaneously with connection of the at least oneelectrical line with the second electrical connector.

The connector assembly may include a dual lumen hose having side-by-sidefirst and second lumens. The first lumen serves as the pneumatic linefor communication of pneumatic pressure from the second pneumatic portof the control unit to the at first pneumatic port of the mattress andthe second lumen serves as an electrical conduit through which the atleast one electrical line is routed. A first end of the dual lumen hosemay be coupled to the dual mode plug. The connector assembly may have apneumatic coupler mounted to the first lumen at a second end of the duallumen hose. The least one electrical line may extend beyond the secondlumen at the second end of the dual lumen hose.

The dual mode plug may include a plug housing and at least one latchmember coupled to the plug housing. The at least one latch member may bemovable between a first position locking the dual mode plug to the mainhousing of the control unit and a second position unlocking the dualmode plug for detachment from the main housing of the control unit. Theat least one latch member may be spring-biased toward the firstposition. The at least one latch member may comprise a pair of latchmembers, each situated on an opposite side of the plug housing. The plughousing may include a pair of recesses and at least a portion of eachlatch member may be received within a respective one of the pair ofrecesses. The pair of latch members may be movable toward the plughousing to move the pair of latch members between the respective firstand second positions.

The dual mode plug may include a front wall. A pneumatic coupler mayextend away from the front wall and an electrical coupler may extendaway from the front wall. The pneumatic coupler may be configured tomate with the second pneumatic port of the control unit and theelectrical coupler may be configured to mate with the second electricalconnector of the control unit. The pneumatic coupler may be formedintegrally with the front wall of the dual mode plug and the front wallof the dual mode plug may have an aperture through which the electricalcoupler extends. The dual mode plug may include a check valve incommunication with the pneumatic coupler.

Additional features, which alone or in combination with any otherfeature(s), such as those listed above and those listed in the claims,may comprise patentable subject matter and will become apparent to thoseskilled in the art upon consideration of the following detaileddescription of various embodiments exemplifying the best mode ofcarrying out the embodiments as presently perceived.

BRIEF DESCRIPTION OF THE DRAWINGS

The detailed description particularly refers to the accompanying figuresin which:

FIG. 1 is an exploded perspective view of a mattress system showinginflatable layers of a mattress of the mattress system situated betweentop and bottom coverlets of the mattress and showing a control unitsituated near a foot end of the bottom of the coverlet coupledelectrically and pneumatically by a connector assembly a technical boxsituated within an interior region of the mattress;

FIG. 2 is a perspective view of the control unit of FIG. 1 showing afirst user interface module being removed from a recess formed in mainhousing of the control unit;

FIG. 3 is a front perspective of the first user interface module of FIG.2 showing user inputs on a front surface of the first user interfacemodule;

FIG. 4 is a front perspective of a second user interface module that iscoupleable to the main housing of the control unit in lieu of the firstuser interface module;

FIG. 5 is a rear perspective of the second user interface module showinga pair of tabs extending from one end of main body of the module and apost extending from an opposite end of the main body of the module andalso showing a lock out switch that is accessible on a rear surface ofthe main body when the module is detached from the control unit;

FIG. 6 is rear perspective view of the control unit showing a latchbeing movable in the direction of the arrow to unlock the user interfacemodule for detachment from the main housing of the control unit;

FIG. 7 a is a side elevation view of the control unit of FIG. 6, withportions broken away, showing the latch in an unlocked position showingthe post situated at an open end of a slot formed in a hook or cam ofthe latch;

FIG. 7 b is a side elevation view, similar to FIG. 7 a, showing thelatch in a locked position such that the post of the user interfacemodule is captured within the slot of the hook;

FIG. 8 is a rear perspective view of the control unit similar to FIG. 6showing a dual mode plug of the connector assembly coupled to a socketprovided in a rear wall of the main housing of the control unit andshowing a coupling hook having a cut out beneath the dual mode plug;

FIG. 9 is a perspective view of the connector assembly showing a duallumen hose having one end coupled to the dual mode plug and havingpneumatic and electrical couplers at an opposite end thereof;

FIG. 10 is an exploded view of the dual mode plug at the end of theconnector assembly that couples to the control unit;

FIG. 11 is an enlarged perspective view of the end of the connectorassembly that couples to the mattress of the mattress system;

FIG. 12 is an enlarged perspective view showing the pneumatic andelectrical couplers of the connector assembly coupled to matingpneumatic and electrical connectors, respectively, included in themattress;

FIG. 13 is a diagrammatic view of the mattress system showing a pressuresensor in a middle region of the mattress and having associated sensorcircuitry, a technical box at a foot end of the mattress having valvesand associated circuitry, and the control unit with its associatedcircuitry;

FIG. 14 is a block diagram showing the logic implemented by thecircuitry of the mattress system to control a bed exit alarm;

FIG. 15 is a block diagram showing the logic implemented by thecircuitry of the mattress system to control a lock out function providedin each of the user interface modules;

FIG. 16 is a perspective view of the control unit of FIG. 1 showing afront shell of the main housing of the control unit pulled away from aback shell of the main housing, a compressor sub-housing situated in thelower region of the back shell, and circuitry of the control unitsituated in the back shell above the compressor sub-housing.

DETAILED DESCRIPTION OF THE DRAWINGS

A mattress system 10 includes a mattress 12 and a control unit 14 thatis spaced-apart from the mattress 12 and that is coupled pneumaticallyand electrically with the mattress 12 by a connector assembly 16 asshown in FIG. 1. As is discussed in greater detail below, the controlunit 14 includes a plurality of user interface modules 50, 52 that areable to be selectively coupled to a main housing 18 of the control unit14 to configure the mattress system 10 with various functionalitiesdepending upon which of the user interface modules 50, 52 is coupled tothe main housing. For example, FIG. 3 shows a user interface module 50having a primary mode of operation that is referred to as a continuouslow pressure mode and FIG. 4 shows a user interface module 52 having aprimary mode of operation that is referred to as an alternating pressuretherapy mode. The illustrative mattress system 10 is availablecommercially and is marketed as the ClinActiv™ Therapy Mattress Systemby Hill-Rom Company, Inc. which is an affiliate corporation of theassignee of the present application.

Illustratively, the mattress 12 includes an upper inflatable bladderlayer 20 having a plurality of laterally-extending cells or bladders 22which cooperate to define various zones of layer 20. For example, a headsection zone includes the first three cells 22 of layer 20. These threecells 22 are fluidly interconnected and are illustratively regulated tothe same pressure. The next ten cells 22 form a torso section zone oflayer 20. Finally, a heel section zone includes the last seven cells 22of layer 20 which are fluidly interconnected with each other and aregenerally regulated to a low target pressure. This target pressure isindependent of the rest of the zones of the layer 20 and is regulated byelectronics within the control unit 14.

When system 10 is operating in the continuous low pressure mode, asdictated by module 50, the ten cells 22 of the torso section zone arecontrolled to the same target pressure. However, when system 10 isoperating in the alternating pressure mode, as dictated by module 52, afirst group of five of the ten cells 22 of the torso section zone aredeflated for a period of time while a second group of five of the tencells 22 of the torso section zone are inflated and then, after theperiod of time and after a dwell time in which all ten cells 22 of thetorso zone section are inflated, the first group of five of the tencells 22 of the torso zone section are inflated for a period of timewhile the second group of five cells 22 of the torso section zone aredeflated for a period of time. This sequence then repeats after anotherdwell time in which all ten cells 22 of the torso section zone areinflated. The cells 22 of the two groups of torso section zone cells 22are arranged such that each cell of the first group is situated betweenadjacent cells of the second group, and vice versa, with the exceptionof the cells that are the head end and foot end of the torso sectionzone. In alternative embodiments, other cells of layer 20 also inflateand deflate alternately in addition to the alternating of the inflationand deflation of the cells 22 of the torso zone section.

In the illustrative example, the head, torso, and heel section zones ofthe layer 20 are controlled and operate independently from one another.Further, while the various head, torso, and heel section zones aredescribed herein as including a particular number of laterally-extendingcells, it is within the scope of this disclosure to include any numberof independently operable zones having any number of interconnectedcells, and having cells of any suitable size, shape, or orientation,including cells that extend longitudinally.

The mattress 12 further includes a first air mattress underlay 24positioned below the layer 20 as well as a second air mattress underlay26 positioned below the first air mattress underlay 24. Thus, underlay24 serves as an intermediate layer between layer 20 and underlay 26.Underlay 24 is a single inflatable bladder but has internal walls orconnections, such as radio frequency welds between top and bottom sheetsof the underlay 24, running in the longitudinal direction of mattress 12to prevent ballooning of underlay 24. Similarly, underlay 26 is also asingle inflatable bladder but has internal walls or connections runningin the lateral direction of mattress 12 to prevent ballooning ofunderlay 26. In the illustrative embodiment, the first air mattressunderlay 24 and the second air mattress underlay 26 are interconnectedvia conduits with each other and with the head section zone of layer 20and are inflated to the same pressure as the head section zone of thelayer 20. The mattress 12 further includes a top coverlet 28 and abottom coverlet 30 which are coupled together by suitable couplers, suchas one or more zippers, to maintain the layer 20 and underlays 24, 26within an interior region of the mattress 12.

Layer 20 and underlays 24, 26 are inflatable patient support elements ofillustrative mattress 12. It should be appreciated that theconstructional details of elements 20, 24, 26 are merely illustrativeand mattress 12 may have inflatable elements of other shapes, sizes, ororientations. Furthermore, mattress 12 may have non-inflatable patientsupport elements, such as foam layers, blocks, pads, and the like, aswell as mesh materials, gel layers, quilting, and the like, in lieu ofor in addition to elements 20, 24, 26. Accordingly, mattresses having noinflatable elements at all are within the scope of this disclosure.

The illustrative mattress 12 further includes a pressure sensor 32 and atechnical box 34 containing an air distribution system 35 which includesa set of valves 37, associated circuitry 39, and a manifold assembly 33in fluid communication with the various cells 22 of layer 20 as well aswith the first and second air mattress underlays 24, 26 as showndiagrammatically in FIG. 13. The manifold assembly 33 includes apneumatic input and a plurality of pneumatic outputs, each of which isassociated its own valve of the set of valves 37. In one embodiment, afirst valve is in fluid communication with the group of five bladders 22of the torso section zone while a second valve is in fluid communicationwith the second group of five bladders 22 of the torso section zone. Thefirst and second sets of bladders 22 in the torso section zone arearranged alternately and the first and second valves 37 are controlledto inflate and deflate the first and second groups of bladders 22 of thetorso section zone alternately when mattress system 10 is operating inthe alternating pressure mode as dictated by the programming of userinterface module 52 as mentioned above. If, on the other hand, userinterface module 50 is coupled to the main housing 18 of control unit14, then the first and second valves 37 are controlled so that all tenof the bladders 22 of the torso zone section remain inflatedsimultaneously to the same target pressure.

The set of valves 37 includes a third valve in fluid communication withthe heel zone of the layer 20 and a fourth valve that is incommunication with the head section zone of the layer 20, the firstmattress underlay 24, and the second mattress underlay 26. The valves 37operate to open and close various passageways of the manifold assembly33 as is appropriate to allow inflation or deflation of the associatedgroups of bladders of mattress 12. In some embodiments, each of thevalves 37 is a three-way valve having an opened position allowingpressurized air to be pumped to the associated bladders 22; a closedposition blocking air from being pumped to, and blocking air fromescaping from, the associated bladders 22 and underlays 24, 26; and avent position allowing air to vent from bladders 22 and underlays 24, 26to atmosphere. In other embodiments, one more of the valves 37 are twoposition valves and a separate vent valve is provided to vent air fromeach of the various groups of bladders as needed. In some embodiments,the valves 37 are solenoid valves. However, other suitable valves, suchas proportional control valves, may be used if desired. The technicalbox 34 further houses circuitry 39, referred to herein sometimes as themanifold printed circuit board (PCB) for controlling the operation ofthe valves 37 within the technical box 34. As is discussed in greaterdetail below, the manifold PCB is in electrical communication with thecontrol unit 14.

Illustratively, the pressure sensor 32 is positioned within a cut-outsection 36 formed in the second air mattress underlay 26 as shown inFIG. 1 while the technical box 34 is positioned at a foot end of themattress 12 such that foot ends of the air mattress underlays 24, 26generally abut the technical box but do not extend over the top of thetechnical box 34. However, the layer 20 (and particularly the heel zonebladders 22 of the layer 20) extends over the technical box 34. When themattress 12 is assembled, the pressure sensor 32 of the mattress 12 ispositioned generally below the torso section zone of the layer 20 inorder to sense the pressure exerted by a patient on the torso sectionzone and provide an output signal to the control unit 14 indicating thesensed pressure.

Mattress 12 includes a cardiopulmonary resuscitation (CPR) assembly thatis coupled to the technical box 34 and that includes a rotatable knob 40that is accessible to the caregiver through an aperture 42 formed in thefoot end portion of the bottom coverlet 30. In normal operation, the CPRknob 40 is in a closed position. When the CPR knob 40 is moved manuallyby a caregiver to an opened position, air rapidly vents through the CPRassembly to atmosphere. In addition, an electrical signal is provided bya switch or other sensor to circuitry 39, the circuitry of control unit14, and the circuitry of sensor 32 to indicate that the CPR knob 40 hasbeen moved to the opened position. In response to this signal, controlunit 14 deactivates operation of the source of a pneumatic pressure 43,such as a compressor, of the control unit 14. A CPR indicator lightflashes on the control unit 14 and a CPR alarm sound beeps regularlyevery 30 seconds to alert the caregiver that the CPR knob 40 has beenactivated. Once activated, the bladders of layer 20 and underlays 24, 26quickly deflate to provide a firm surface for performing CPR on thepatient lying atop the mattress 12.

Illustratively, the pressure sensor 32 of the mattress 12 comprises aliquid-containing flexible enclosure 45 and associated circuitry 47 asshown in FIGS. 1 and 13. Enclosure 45 and circuitry 47 are both situatedin the cut-out section 36 of underlay 26. In some embodiments, theliquid-containing enclosure 45 comprises a bag or bladder filled with asilicon oil, such as polydimethylsiloxane. Circuitry 47 includes apressure transducer which is exposed to the fluid pressure in the bagvia a conduit. The transducer of circuitry 47 detects the pressureexerted upon it by the liquid and relays a pressure signal to thecontrol unit 14 via circuitry 47 and circuitry 39. The pressure sensedby the transducer correlates to the amount of weight and pressureexerted on enclosure 45, which correlates to the weight of the patienton the mattress. As is discussed in greater detail below, circuitrywithin the control unit 14 operates to establish the target pressures ofthe zones of layer 20 and underlays 24, 26 and also determines whetherone or more zones of the layer 20 are to be inflated or deflated basedupon information received from the pressure signal. The principles ofoperation of the pressure sensor 32 is described in greater detail inU.S. Pat. No. 6,094,762 which is owned by the same assignee as thepresent application and which is hereby incorporated by referenceherein.

As mentioned above, the pressure sensor 32 is positioned below the torsosection zone of layer 20. Accordingly, as the patient's torso appliespressure on the mattress 12, this pressure is transferred as a force tothe enclosure 45 of pressure sensor 32. The pressure in the enclosure 45is detected by the transducer of circuitry 47 and a pressure signal issent to the control unit 14. Circuitry within the control unit 14 thendetermines whether to vent air from the layer 20 and/or underlays 24, 26of the mattress 12 or to turn on the pneumatic source 43 within thecontrol unit 14 to inflate the layer 20 and/or underlays 24, 26 in orderto reach respective target pressures which are established by controlunit 14 based on the signal received from sensor 32. Accordingly, thetarget pressures of cells 22 of layer 20 and underlays 24, 26 of themattress 12 are adjusted automatically to accommodate each individualpatient's weight and position. In some embodiments, a pressurecomparator is provided in circuitry 47 to make a comparison between thepressure in enclosure 45 and the pressure in the head section zonebladders 22 of layer 20 and the underlays 24, 26 and then control unit14 and valves 37 are operated to equalize the pressure therebetween. Insuch an arrangement, any additional pressure sensor to sense thepressure in head section zone bladders 22 of layer 22 and underlays 24,26 may be omitted.

In some embodiments, additional pressure sensors 41 are provided intechnical box 34 and are associated with respective pneumatic lines usedto inflate layer 20 and underlays 24, 26. The additional pressuresensors detect and communicate the pressure within each zone of thelayer 20 and within the underlays 24, 26 to the control unit 14. Suchmeasured pressures are compared with the target pressure valuesestablished by the circuitry of control unit 14 based on the pressuresignal originating from pressure sensor 32. In other embodiments,technical box 34 has only a single pressure sensor 41 which is coupledsequentially, by appropriate opening and closing of the various valves37, to each of the zones of layer 22 and to underlays 24, 26 to measuresequentially the pressures in each of the zones.

The data from pressure sensor 32 is used in three distinct operationmodes of system 10 including stand-by regulation, patient egresssurveillance, and main zone pressure regulation. As is discussed ingreater detail below, the stand-by regulation mode means that system 10operates to achieve a relatively low pressure in the mattress 12 so asto provide a ready-to-use, and yet comfortable, support when the patientis initially placed on the mattress 12. The patient egress surveillancemode means that system 10 operates to monitor the presence and absenceof the patient on the mattress 12. The main zone pressure regulationmode means that system 10 operates to control the internal pressures inthe bladders 22 of layer 20 and underlays 24, 26. Illustratively, thecircuitry 47 of pressure sensor 32 is in electrical communication withthe circuitry 39 situated within the technical box 34. As noted above,the circuitry 39 within the technical box 34 is in electricalcommunication with the control unit 14 via the connector assembly 16.

Referring now to FIGS. 2-6, the control unit 14 includes the mainhousing 18, a source of pneumatic pressure 43 such as a pump, blower, orcompressor (shown diagrammatically in FIG. 13) contained within the mainhousing 18, and first and second user interface modules 50, 52 that areselectively coupleable to the main housing 18. The compressor 43 of thecontrol unit 14 is enclosed in a sub-housing 49, shown in FIG. 16,within the main housing 18 of the control unit 14 to dampen noise whilethe compressor 43 is running. Power is provided to unit 14 via a powercord 19, shown in FIG. 1, which plugs into unit 14 and into a standardelectrical outlet to receive power therefrom. Illustratively, thesub-housing 49 is made of aluminum; however, is should be understoodthat the sub-housing 49 may be made of other suitable materials todampen the noise of the compressor 43 contained therein. Further, an airchamber 51 of the control unit 14 is positioned generally in top regionof the compressor sub-housing 49 in order to serve as a pressurereservoir that stabilizes the air flow within the control unit 14 aswell as reduce noise output of the control unit 14.

Each of the first and second user interface modules 50, 52 areprogrammed to control inflation of the layer 20 and/or underlays 24, 26of the mattress 12 differently in various operational modes of each ofinterface module 50, 52. Illustratively, the front side of the mainhousing 18 includes a recess 54 provided therein. The interface modules50, 52 are each selectively received within the recess 54 and are lockedin place by a latch 90 of the control unit 14, as is discussed ingreater detail below with regard to FIGS. 7 a and 7 b. The userinterface modules 50, 52 operate as the main caregiver controls of themattress system 10 while also providing feedback to the caregiver as tothe operational status of the system 10. Each of the modules 50, 52includes circuitry that is programmed with instructions that dictate theoperational modes of system 10.

Referring to FIG. 3, the first user interface module 50 includes a userinterface panel 55 having a front surface 56 and a main body 57 that iscoupled to the user interface panel 55 and that has a rear surface 58.Illustratively, the first user interface module 50 is a continuous lowpressure (CLP) therapy module. The CLP mode of the module 50 isautomatically activated when the CLP module 50 is placed in the recess54 of the control unit 14 and the main switch 53 of control unit 14 (seeFIG. 16) is switched on. Illustratively, the CLP module 50 and module 52each include an electrical connector 59 on the rear surface 58 of themain housing 57 as shown in FIG. 5 with regard to module 52. Theelectrical connector 59 is coupled to an electrical coupler 61, shown inFIG. 2, within the recess 54 of the control unit 14 to provideelectrical communication between the module 50 and internal circuitry63, shown in FIG. 16, of the control unit 14. A ribbon cable 65, alsoshown in FIG. 16, interconnects connector 61 and circuitry 63.

During the CLP mode, the ten cells 22 in the torso section of the layer20 are regulated to the same target pressure (all targets pressuresreferred to herein have associated tolerance ranges as is well known inthe art) as set by the pressure sensor 32. As mentioned above, the threehead section cells 22 of the layer 20, the first underlay mattress 24,and the second underlay mattress 26 are fluidly interconnected with eachother and are inflated to the same pressure as the cells 22 of the torsosection of the layer 20 during the CLP mode. The seven foot sectioncells 22 of the layer 20 are regulated to a lower target pressure whichis determined independently of the rest of the mattress sections.

Various user inputs and indicators are provided on the front surface 56of the user input panel 55 of the module 50 as shown in FIG. 3. Forexample, an on/off button 58 is engaged by a user to turn the module 50on or off. A light indicator 60 illuminates to denote that the module 50has been turned on. Upon first connecting the control unit 14 to themain power supply, the mattress system 10 operates to automaticallyinflate the layer 20 and underlays 24, 26 to a maximum inflationpressure value to fully expand the cells 22 and underlays 24, 26. Themattress system 10 then automatically reverts to the therapy modeprovided by the selected module 50 or 52 after approximately eightminutes. During start up, the caregiver may press the on/off button 58twice to override the maximum inflation function, if desired.

An internal pressure indicator provides an indication of the pressurevariation in the torso zone of the layer 20. Segments of the lightindicator 62 will illuminate as the pressure within the torso zoneautomatically varies. A maximum inflation (P-max) button 64 is engagedby user to inflate layer 20 and underlays 24, 26 to the maximuminflation pressure at the user's discretion. Thus, the maximum inflationbutton 64 may then be activated at any time in order to inflate thelayer 20 and underlays 24, 26 to the maximum inflation pressure.Oftentimes, for example, a caregiver may use the maximum inflate button64 in order to provide a firmer patient support surface for patienttransfers or bedding changes. Illustratively, pressing the maximuminflation button 64 a second time will immediately end the maximuminflation mode and return the mattress 12 to the therapy mode. Themaximum inflation pressure is a target pressure that is typically higherthan the pressures to which layer 20 and/or underlays 24, 26 areinflated during other modes of operation of system 10 and it should beunderstood that layer 20 and underlays 24, 26 are capable ofwithstanding even higher pressures than the one referred to as themaximum inflation pressure in this disclosure.

Pressing a bed exit alarm button 66 of the user interface module 50 armsor enables a patient egress surveillance system (sometimes referred toherein as a “bed exit system” or “bed exit alarm system” or the like).As is discussed in greater detail below, the pressure sensor 32 of themattress 12 operates to detect the presence and absence of a patient onthe mattress 12 by sending a pressure signal to the control unit 14.Circuitry of the control unit 14 then determines, based upon the valueof the pressure signal, whether the patient is present on, or absentfrom, the mattress 12. The determination regarding the presence ofabsence of the patient is made by comparing the pressure sensed bysensor 32 with a threshold value. If it is determined that the patientis absent from the mattress 12, an alarm to alert a caregiver isactivated if the bed exit alarm system is enabled. The alarm may be avisual alarm such as a light indicator on the module 50 and/or may be anaudible alarm such as a beeping noise made by a sound-producing devicesuch as a speaker or piezoelectric buzzer, for example. When the bedexit alarm function is enabled, a light indicator 68 on the module 50 isilluminated.

An alarm silence button 70 of the module 50 may be engaged by a user totemporarily silence any audible alarm associated with the maximuminflation function, the CPR function, a power failure, and/or a mattressmalfunction. For example, when one or more of the above-referencedalarms are sounding, the caregiver may press the alarm silence button 70to temporarily silence the sounding alarm(s). The alarm(s) will thensound again after approximately 10 minutes if the condition causing thealarm is not rectified. The alarm(s) may also be permanently silenced bypressing the alarm silence button 70 until the light indicator 72flashes. In some embodiments, the alarm silence button 70 also may beengaged by the user to silence a bed exit alarm.

A CPR light indicator 74 of the module 50 flashes when the CPR function,discussed above, is activated. A seat cushion light indicator 76illuminates when an optional seat cushion (not shown) of the mattresssystem 10 is being inflated. The indicator 76 turns off afterapproximately five minutes once the seat cushion is completely inflated.Illustratively, during inflation of the seat cushion, the maximuminflation function is automatically activated without audibleindication. The seat cushion inflation may be stopped at any time bypressing the maximum inflation button 64. Once inflated, the seatcushion is disconnected from control unit 14 and remains inflated foruse on a wheel chair or other type of seating surface. A valve coupledto the seat cushion may be open to allow deflation of the seat cushionto atmosphere.

A safety lock-out light indicator 78 of the module 50 illuminateswhenever the user interface module 50 is locked-out to prevent a patientor caregiver from adjusting the settings. Illustratively, as shown inFIG. 5 with regard to module 52, the rear surface of the module 50 andthe module 52 each includes a lock-out switch 80. The caregiver may movethe lock-out switch 80 to an activated position in order to lock-out thecontrols of the module 50 or the module 52, as the case may be, toprevent a patient or other caregiver from tampering with the particularsettings of the module 50, 52, thereby to prevent intentional orunintentional changes in the operating mode of system 10.Illustratively, the lock-out switch 80 is located on the rear surface 58of the module 50, 52 and is, therefore, generally inaccessible by thepatient. The safety lock-out indicator 78 is illuminated when thelock-out switch 80 has been activated. Illustratively, the safetylock-out indicator light 78 will then flash in the event of a controlbutton being pressed in order to signal that the user interface islocked-out.

To unlock the lock-out function, the caregiver removes the module 50from the housing 18 of the control unit 14 and moves the lock-out switch80 to the deactivated or unlocked position. Alternatively, the caregivermay temporarily unlock the lock-out function by removing the module 50from the housing 18 and pressing a lock-out button 81 adjacent theswitch 80. Illustratively, pressing the lock-out button 81 (whilemaintaining the switch 80 in the activated position) operates todeactivate the lock-out function for a predetermined period of time,such as 20 seconds, for example. This function allows the user then toresecure the module 50 to the housing 18 and manipulate the controls ofthe module 50 without having to again remove the module 50 from thehousing to reinitiate the safety lock-out function. Once the caregiverhas manipulated the controls of the module 50, the lock-out functionwill be automatically reactivated once the predetermined period of timehas elapsed.

A power failure light indicator 82 illuminates when the control unit 14is disconnected from the main power supply or in the event of a powerfailure. The power failure light indicator 82 will also illuminateduring transport. A mattress malfunction light indicator 84 of module 50illuminates in the event of a pressure fault and a continuous lowpressure (CLP) therapy indicator 86 of module 50 illuminates to indicatethat CLP therapy is being used.

Illustratively, as noted above, an audible alarm is sounded, as well asa visual indicator being illuminated, when the maximum inflationfunction has been activated, when the CPR function has been activated,when a patient has exited the bed (assuming the bed exit alarm system isenabled), when the control unit 14 has been disconnected from the mainpower supply or when a power failure has occurred, and when a mattressdefect is detected.

Referring now to FIG. 4, the second user interface module 52 similarlyincludes the user interface panel 55 having the front surface 56 and themain body 57 having the rear surface 58. Illustratively the second userinterface module 52 is an alternating pressure (AP) therapy module. TheAP therapy mode is automatically activated when the AP module 52 isplaced within the recess 54 of the main housing 18 of the control unit14. Illustratively, the AP mode affects the ten cells 22 within thetorso section zone of the layer 20 to sequentially inflate and deflateevery other cell 22 within the torso section zone. Accordingly, none ofthe three head section cells 22 and none of the seven heel section cells22 are alternately inflated and deflated in the illustrative embodiment,but may do so in other embodiments.

As noted above, the pressure in the torso section cells 22 is controlledby the pressure sensor 32. Illustratively, the AP mode may be describedin three phases. In the first phase, five non-adjacent cells 22 (forminga first AP zone of cells) in the torso section zone of the layer 20 aredeflated. This deflation takes approximately four minutes. In the secondphase, the pressure in all the cells 22 within the torso section is thesame (i.e., at a continuous low pressure). The duration of the secondphase is approximately 1 minute. The purpose of the second phase of theAP therapy mode is to enhance patient comfort by providing a softsurface between the deflated phases. In the third phase, the other fivenon-adjacent cells 22 (forming a second AP zone of cells) in the torsosection zone of the layer 20 are deflated. Similar to the first phase,the third phase lasts approximately four minutes. A similar discussionof the AP mode is presented above.

Various user inputs and indicators are provided on the front surface 56of the user input panel 55 of the module 52. Illustratively, many ofthese user inputs are the same as those discussed above with respect tothe first user interface module 50. As such, like reference numeralshave been used to denote like inputs and/or indicators. However, ratherthan including the CLP indicator 86 of the module 50, the module 52includes an alternating pressure (AP) therapy indicator 88 to indicatethat AP therapy is being used.

Although the CLP user interface module 50 and the AP user interfacemodule 52 are provided in the illustrative examples, it is within thescope of this disclosure for the mattress system 10 to include otheruser interface modules that are selectively coupleable with the controlunit 14 as well. For example, a rotation therapy user interface modulemay provide a continuous lateral rotation therapy (CLRT) function and alow air loss user interface module may provide a low air loss functionfor cooling the patient and/or wicking moisture away from the patient.Of course, it should be understood that any number of user interfacemodules having any number of therapy functions may be provided for usewith the control unit 14 and mattress 12 of the mattress system 10.Further, it is within the scope of this disclosure to include more thanone therapy function on a single user interface module. For example,while each of the CLP and AP modules 50, 52 are dedicated to a singletherapy, a single user interface module may be provided which includesboth CLP and AP therapies. Accordingly, any number and any combinationof desired therapies may be provided on a single user interface module.Each user interface module includes circuitry that is programmed toimplement its associated functionalities. Thus, the programming of thevarious types of modules is different. This provides a cost savings tohealthcare facilities because, to achieve different types of patienttherapies, only the associated user interface modules need to bepurchased rather than having to purchase an entirely different mattresssystem.

Each of the user interface modules 50, 52 further includes a lockingpost 92 extending from a first end of 94 the main body 57 of therespective module 50, 52, as shown in FIGS. 3 and 4. Referring now toFIG. 5, a pair of tabs 96 of each user interface module 50, 52 extendoutwardly from a second end 98 of the main body 57 of the respectivemodule 50, 52. Thus, post 92 and tabs 96 extend from main body 57 inopposite directions. As is discussed below, the locking post 92 and tabs96 are used to secure the respective modules 50, 52 within the recess 54formed in the main housing 18 of the control unit 14.

As noted above, the user interface modules 50, 52 may be selectivelyattached to and removed from the main housing 18 of the control unit 14.In order to attach one of the first and second user interface modules50, 52 to the main housing 18 of the control unit 14, the caregiverslides the pair of tabs 96 of the selected module 50 or 52 intocorresponding slots 67, shown in FIG. 2 (in phantom), formed in the mainhousing 18 of the control unit 14. In the illustrative embodiment, theslots of the housing 18 are formed in a side wall of housing 18 definingpart of the recess 54. Once the tabs 96 of the selected module 50 or 52are received within the corresponding slots of the housing 18, the mainbody 57 of the selected module 50 or 52 may further moved into therecess 54 such that the locking post 92 is received within a slot 97defined by hook portion 98 of a pivotable cam 99 coupled to the latch 90to further secure the selected module 50 or 52 within the housing 18.Illustratively, as shown in FIGS. 7 a and 7 b, movement of the latch 90in a first direction 101 operates to rotate the cam 99 in a clockwisedirection such that the slot 97 of the hook portion 98 captures the post92 of the selected module 50 or 52 therein (as shown in FIG. 7 b).

In order to remove one of the first and second user interface modules50, 52 from the control unit 14, the caregiver may rotate the latch 90located at the rear side of the control unit housing 18 in direction 103shown in FIG. 7 b from a first, locked position to a second, unlockedposition. Illustratively, movement of the latch 90 in direction 103operates to rotate the cam 99 in a counterclockwise direction such thatthe post 92 of the selected module 50 or 52 becomes disengaged from theslot 97 of the hook portion 98 (as shown in FIG. 7 a). When the latch 90is in the second, unlocked position, hook 98 of the cam 99 is disengagedfrom the post 92 of the selected module 50 or 52 to allow the caregiverto remove the particular user interface module 50 or 52 from the mainhousing 18 of the control unit 14.

The shape of slot 97 is such that when latch 90 is rotated in direction101, with hook portion 98 capturing post 92, post 92 is pulled generallyradially inwardly toward the pivot axis of latch 90 to firmly seat theassociated module 50, 52 against the main housing 18 and to pull theelectrical connectors 59, 61 together. On the other hand, when latch 90is rotated in direction 103, with hook portion 98 capturing post 92,post 92 is pushed generally radially outwardly way from the pivot axisof latch 90 to unseat the associated module 50, 52 from housing and topush the electrical connectors 59, 61 apart. After being unseated inthis manner, the module 50, 52 is far enough away from main housing 18to provide space for a user to grasp the module 50, 52, as shown in FIG.7 a with regard to module 50, and completely detach it from housing 18.

Referring now to FIG. 8, the control unit 14 further includes a socket100 formed in a rear wall 102 of the main housing 18 as well as abracket assembly or coupling hook 104 coupled to the rear side 102 ofthe main housing 18. As is discussed in greater detail below, the socket100 of control unit 14 receives a dual mode plug 110 of the connectorassembly 16 therein. Illustratively, the coupling hook 104 is positionedbelow the socket 100 of the main housing 18 and is provided to allow acaregiver to hang the control unit 14 on a footboard or side rail of abed frame, for example. Hook 104 has a cutout 101 to accommodate thedual mode plug 110 and a user's fingers when attaching the connectorassembly 16 to, or detaching the connector assembly 16 from, housing 18.The control unit 14 also includes rubber pads (not shown) on a bottomsurface of the main housing 18 in order to enable the control unit 14 tostand on a hard surface as well.

Referring now to FIGS. 9-12, the connector assembly 16 of the mattresssystem 10 provides a pneumatic and electrical connection between thecontrol unit 14 and the mattress 12. The connector assembly 16 includesa dual lumen hose 118 including a pneumatic line 120 for communicationof pneumatic pressure from the control unit 14 to the mattress 12 and anelectrical line 122 that serves as an electrical conduit through whichelectrical conductors are routed between the control unit 14 and themattress 12. Illustratively, the pneumatic line 120 and the electricalline 122 are connected to each other and positioned side-by-side along amajority of the length of the lines 120, 122, as shown in FIG. 9, forexample.

The connector assembly 16 further includes the dual mode plug 110 at afirst end of the dual lumen hose 118. The dual mode plug 110 is receivedwithin the socket 100 of the main housing 18 in order to provide asubstantially simultaneous pneumatic and electrical connection with thecontrol unit 14. Illustratively, the dual mode plug 110 includes a plughousing 124 and two latch members 126 coupled to respective sides of theplug housing 124. In particular, the plug housing 124 includes a pair ofrecesses 127 formed in each side of the plug housing 124 such that aportion of each latch member 126 is received within a respective recess127. Each of the latch members 126 are movable between a first positionlocking the dual mode plug 110 to the main housing 18 of the controlunit 14 and a second position unlocking the dual mode plug 110 from themain housing 18 of the control unit 14. Illustratively, the latchmembers 126 are spring-biased toward the first position by respectivesprings 128, shown in FIG. 10. Further, in order to move the latchmembers 126 between the first and second positions, a caregiver squeezeseach latch member 126 in a direction generally toward the plug housing124 and further within the respective recesses 127.

Referring still to FIG. 10, the dual mode plug 110 further includes afront wall 130 coupled to the housing 124, a pneumatic coupler 132extending away from the front wall 130, and an electric coupler 134 thatextends beyond front wall 130 through an aperture 133 formed therein. Afirst end of each of the electrical conductors routed through line 122is coupled to, and terminates at, electrical connector 134. The controlunit 14 includes an electrical connector 107 (shown diagrammatically inFIG. 13) within the socket 100 which is in communication with theinternal circuitry 63 control housing 14 and a pneumatic port 109 (alsoshown diagrammatically in FIG. 13) within the socket 100 which is incommunication with the compressor 43 of the control unit 14.Accordingly, when the dual mode plug 110 is received within the socket100 of the control unit 14, the pneumatic coupler 132 of the plug 110 iscoupled to the pneumatic port 109 of the control unit 14 and theelectric coupler 134 of the plug 110 is coupled to the electricalconnector 107 of the control unit 14. Further, the dual mode plug 110 isconfigured so that the electrical and pneumatic connections between theconnector assembly 16 and the control unit 14 are made substantiallysimultaneously.

A check valve 131 is provided within housing 124 of plug 110 and is inpneumatic communication with port 132. When plug 110 is coupled tosocket 100 and compressor 43 is operated, the check valve 131 is openedto allow pressurized air to move through pneumatic line 120. When plug110 is disconnected from socket 100, check valve 131 is closed toprevent air from escaping from mattress 14 through connector assembly16.

Latch members 126 each have a rearwardly projecting tab 111 that iscaptured within a rear pocket 121 of the respective recess 127 and aforwardly projecting tab 113 that extends through a respective aperture115 of front wall 130. Apertures 115 are oversized in the lateraldirection to allow movement of tabs 113 therein when latch members 126move between the first and second positions. Each latch member 126 alsohas a laterally inwardly projecting tab 117 that is received in anassociated slot 119 formed in a respective side of housing 124. Receiptof tabs 111, 113 in the associated pockets 121 and apertures 115 retainslatch members 126 in place within recess 127, whereas receipt of tabs117 in slots 119 guides the lateral movement of latch members 126. Eachof latch members 126 further has a laterally outwardly projecting tabs123 that is received in associated tab-receiving recess or pocket 125,shown in FIG. 8 (in phantom), formed in the sidewalls of socket 100.Receipt of tabs 123 in recesses 125 locks plug 110 to the socket 100 ofthe housing 18 of the control unit 14. When latch members 126 aresqueezed toward housing 124 of plug 110, tabs 123 are withdrawn fromrecesses 125, thereby allowing plug 110 to be disconnected from socket100.

Referring now to FIGS. 9 and 11, the connector assembly 16 furtherincludes a pneumatic coupler 140 mounted to the second end of thepneumatic line 120 and an electrical connector 142 mounted to an end ofa cable 141 of the electrical conductors which exit from the second endof the electrical line 122. As shown in FIG. 12, the pneumatic coupler140 is coupled to a pneumatic port 144 of the mattress 12. Specifically,the technical box 34 includes the pneumatic port 140 which is inpneumatic communication with the inflatable layer 20 and underlays 24,26 of the mattress 12 via the manifold assembly 35 within the technicalbox 34. Further, the electrical connector 142 of the connector assembly16 is coupled to an electrical connector 146 of the technical box 34 ofthe mattress 12. The electrical connector 146 of the mattress 12 is inelectrical communication with the electrical circuitry 39, 47 within themattress 12. Further illustratively, the technical box 34 includes afirst pressure test port 150 for checking the pressure in the torso zoneof the layer 20 and a second pressure test port 152 for checking thepressure in the heel zone of the layer 20. Pressure transducers 41 oftechnical box 34 are coupled electrically to test ports 150, 152 toprovide feedback information regarding the pressure within an associatedzone of mattress 14.

In operation, air enters the control unit 14 through an air filter (notshown) within the control housing 18 of the control unit 14. The airthen travels into the compressor inlet. Upon exiting the compressor 43,the air travels through check valve 131 and the pneumatic line 120 ofthe connector assembly 16 and into the manifold assembly 35 located inthe technical box 34 within an interior region of the mattress 12. Theair is then dispatched through valves 37 into the various inflatablemattress layers including the layer 20, the first air mattress underlay24, and the second mattress underlay 26. In the illustrative embodiment,the check valve 131 located inside plug 110 of the connector assembly 16provides approximately four hours of inflation of the mattress 12 in theevent the control unit 14 is disconnected from the main power supply orif the dual lumen hose 118 is disconnected from the control unit 14.

As mentioned above, each of modules 50, 52 is programmed to providesystem 10 with a bed exit alarm function. FIG. 14 is a diagram whichillustrates the logic of the bed exit alarm function of system 10.Sensor 32 provides a signal to circuitry 47 which measures the pressureexerted on sensor 32 as indicated at block 160. A comparator 162receives the pressure measurement signal and also receives a thresholdsetting signal which is represented by block 164 in FIG. 14. In oneembodiment, the threshold setting is established for a minimum patientweight of fifty pounds but, in other embodiments, other thresholdsettings may be established at the discretion of the system programmeror designer.

If the pressure measurement signal is less than the threshold valuesignal, which is an indication that the patient has exited the mattress14, then the output of comparator 162 is on (e.g., a high logic state),otherwise the output of comparator 162 is off (e.g., a low logic state).If the comparator is turned on, then system 10 automatically operates inthe stand by mattress pressure regulation mode in which layer 20 andunderlays 24, 26 are controlled to reduced pressure settings asindicated at block 166. If the bed exit or patient egress alarm isenabled, as indicated at block 168 and the comparator is on, then theoutput of an AND gate 170 is on. The output of AND gate 170 is input toanother AND gate 172 which has a second input from a 1 Hertz (Hz) clock174. Thus, if the output of AND gate 170 is on, then the output of ANDgate 172 will be a 1 Hz signal that is fed to patient egress alarmindicator as indicated at block 176.

As mentioned above the bed exit alarm may include a visual indicator,such as a light emitting diode (LED) and/or a sound producing device,such as a speaker or buzzer. In the illustrative embodiment, the 1 Hzsignal being output from AND gate 172 will cause the visual indicator toflash at a rate of 1 Hz and will cause the sound producing device tobeep at a rate of 1 Hz. Although, logical AND gates 170, 172 are used inFIG. 14 to explain the operation of the bed exit alarm function ofsystem 10, it should be appreciated that the logical AND conditions maybe implemented by software rather than by use of discrete logic gates,but use of discrete logic gates is within the scope of the disclosure aswell.

As mentioned above, each of modules 50, 52 includes lock-out switch 80and lock-out button 81 which are used to lock out various functions ofthe modules 50, 52 and to unlock the functions. FIG. 15 is a diagramwhich illustrates the logic of the lock out function of system 10. Whenswitch 80 is in its position enabling various functions of system 10, anoutput of an OR gate 178 is turned on (i.e., a high logic state) and iscoupled to the input of a set of AND gates 180, each of which isassociated with a respective function as indicated generically at a“function A” block 182 and at a “function Z” block 184 in FIG. 15. A“function key A” switch 186 is coupled to the input of the AND gate 180associated with function A and a “function key Z” switch 188 is coupledto the input of the AND gate 180 associated with function Z. Function Aand function Z are intended to generically represent the functions ofsystem 10. The dotted lines appearing in FIG. 15 between switches 186,188 and between the output of OR gate 178 and the AND gate associatedwith function Z are intended to convey the notion that additionalfunctions may be controlled in the same manner as the two that areillustrated.

When the output of OR gate 178 is on, which occurs when system 10 isenabled, and button 186 or button 188 is pressed, the associated ANDgate has two high logic states at its input resulting in its associatedoutput being turned on (i.e., a high logic state) to signal theoperation of the associated function A or function Z. If switch 80 is inits position disabling or locking out the various functions of system10, and assuming button 81 is not pressed, then both inputs to OR gate178 are at low logic states and the output of OR gate 178 is off (i.e.,a low logic state) resulting in the output of the associated AND gates180 being turned off, regardless of whether either of buttons 186, 188is pressed.

If switch 80 is in its position locking out the various functions ofsystem 10 and switch 81 is pressed, then a twenty second timer isactivated, as indicated at block 190, resulting in a high logic statebeing applied at one of the inputs of OR gate 178 for twenty seconds,thereby turning the output of OR gate 178 on, thereby enabling thevarious functions of system 10 for twenty seconds. During this twentyperiod, switches 186, 188 may be pressed to operate the associatedfunction 182, 184. After the expiration of the twenty second timer, theOR gate 178 once again receives two low logic inputs which turns off theoutput of the OR gate 178 thereby locking out the functions of system10.

Switches 186, 188 are coupled to the inputs of an OR gate 192 as shownin FIG. 15. The output of OR gate 192 is coupled to a lock light 194.Lock light 194 is turned on by OR gate 192 when switch 80 is in itsposition locking out the functions of system 10 and lock light 194flashes if either of switches 186, 188 is pressed when system 10 islocked out. Although, logical AND gates 180 and logical OR gates 178,192 are used in FIG. 15 to explain the operation of the lock outfunction of system 10, it should be appreciated that the logical AND andlogical OR conditions may be implemented by software rather than by useof discrete logic gates, but use of discrete logic gates is within thescope of the disclosure as well.

Although certain illustrative embodiments have been described in detailabove, variations and modifications exist within the scope and spirit ofthis disclosure as described and as defined in the following claims.

1. A mattress system comprising a mattress including at least oneinflatable bladder and a pressure sensor situated within an interiorregion of the mattress, and a control unit spaced from the mattress andhaving circuitry that receives a signal from the mattress which isindicative of a pressure sensed by the pressure sensor, the circuitryusing the signal to establish at least one target pressure to which theat least one inflatable bladder is controlled and the circuitry alsousing the signal to determine whether to activate a bed exit alarm. 2.The mattress system of claim 1, wherein the pressure sensor comprises abag filled with silicon oil.
 3. The mattress system of claim 2, whereinthe mattress comprises an inflatable underlay having a space thatreceives the bag filled with silicon oil.
 4. The mattress system ofclaim 1, wherein the at least one inflatable bladder comprises at leastone inflatable layer that overlies the pressure sensor.
 5. The mattresssystem of claim 4, wherein the at least one inflatable layer comprisesfirst and second inflatable layers that overlie the pressure sensor. 6.The mattress system of claim 5, wherein the first inflatable layercomprises a plurality of laterally extending air bladders, at least twoof which are inflatable to different pressures, and the secondinflatable layer extends approximately the full length of the mattressand is inflatable to a single target pressure.
 7. The mattress system ofclaim 1, wherein the bed exit alarm comprises a flashing light that iscarried by the control unit.
 8. The mattress system of claim 1, whereinthe bed exit alarm comprises a sound-producing device carried by thecontrol unit.
 9. A mattress system comprising a mattress having at leastone inflatable bladder, at least one electrical component situatedwithin an interior region of the mattress, a first pneumatic port incommunication with the at least one inflatable bladder, and a firstelectrical connector in communication with the at least one electricalcomponent, a control unit spaced from the mattress and comprising a mainhousing, a source of pneumatic pressure carried by the main housing andoperable to inflate the at least one inflatable bladder, and circuitryprogrammed to control the manner in which the at least one inflatablebladder is inflated, the circuitry including a second electricalconnector, the control unit including a second pneumatic port incommunication with the source of pneumatic pressure, and a connectorassembly to pneumatically connect the first pneumatic port with thesecond pneumatic port and to electrically connect the first electricalconnector with the second electrical connector, the connector assemblyincluding a pneumatic line, at least one electrical line, and a dualmode plug configured to permit connection of the pneumatic line with thesecond pneumatic connector substantially simultaneously with connectionof the at least one electrical line with the second electricalconnector.
 10. The mattress system of claim 9, wherein the connectorassembly includes a dual lumen hose having side-by-side first and secondlumens, the first lumen serves as the pneumatic line for communicationof pneumatic pressure from the second pneumatic port of the control unitto the at first pneumatic port of the mattress and the second lumenserves as an electrical conduit through which the at least oneelectrical line is routed.
 11. The mattress system of claim 10, whereina first end of the dual lumen hose is coupled to the dual mode plug,wherein the connector assembly has a pneumatic coupler mounted to thefirst lumen at a second end of the dual lumen hose, and wherein the atleast one electrical line extends beyond the second lumen at the secondend of the dual lumen hose.
 12. The mattress system of claim 9, whereinthe dual mode plug includes a plug housing and at least one latch membercoupled to the plug housing, the at least one latch member being movablebetween a first position locking the dual mode plug to the main housingof the control unit and a second position unlocking the dual mode plugfor detachment from the main housing of the control unit.
 13. Themattress system of claim 12, wherein the at least one latch member isspring-biased toward the first position.
 14. The mattress system ofclaim 12, wherein the at least one latch member comprise a pair of latchmembers, each situated on an opposite side of the plug housing.
 15. Themattress system of claim 14, wherein the plug housing includes a pair ofrecesses and at least a portion of each latch member is received withina respective one of the pair of recesses.
 16. The mattress system ofclaim 14, wherein the pair of latch members are movable toward the plughousing to move the pair of latch members between the respective firstand second positions.
 17. The mattress system of claim 9, wherein thedual mode plug includes a front wall, a pneumatic coupler extending awayfrom the front wall, and an electrical coupler extending away from thefront wall; wherein the pneumatic coupler is configured to mate with thesecond pneumatic port; and wherein the electrical coupler is configuredto mate with the second electrical connector.
 18. The mattress system ofclaim 17, wherein the pneumatic coupler is formed integrally with thefront wall and the front wall has an aperture through which theelectrical coupler extends.
 19. The mattress system of claim 17, whereinthe dual mode plug includes a check valve in communication with thepneumatic coupler.
 20. A mattress system comprising a mattress having atleast one person support element, a pressure sensor situated within aninterior region of the mattress, the pressure sensor being situatedbeneath the at least one person support element and comprising anenclosure containing a liquid, and circuitry that receives a signal fromthe pressure sensor and that determines, based on the signal, whether abed exit condition has been detected.
 21. The mattress system of claim20, wherein the at least one person support element comprises at leastone foam element.
 22. The mattress system of claim 20, wherein the atleast one person support element comprises a plurality of foam elements.23. The mattress system of claim 20, wherein the at least one personsupport element comprises at least one foam element and at least oneinflatable bladder.
 24. The mattress system of claim 20, wherein theliquid contained in the enclosure comprises a silicon oil.
 25. Themattress system of claim 20, wherein the liquid contained in theenclosure fills substantially all of an interior region of theenclosure.
 26. The mattress system of claim 20, wherein the enclosurecomprises a flexible bag.
 27. The mattress system of claim 20, whereinthe mattress further comprises an underlay that is situated beneath theat least one person support element and that has a space which receivesthe enclosure containing the liquid.
 28. The mattress system of claim20, wherein the circuitry includes a sound-producing device that isactivated if the circuitry determines that a bed exit condition has beendetected.
 29. The mattress system of claim 20, wherein the circuitry ispositioned within the mattress.
 30. The mattress system of claim 20,further comprising a control unit having a housing spaced from themattress, the circuitry is carried by the housing, and the pressuresensor is operably coupled to the circuitry.
 31. The mattress system ofclaim 30, wherein the pressure sensor is operably coupled to thecircuitry via at least one electrical line that extends from themattress to the control unit.
 32. The mattress system of claim 30,wherein the pressure sensor is operably coupled to the circuitry via awireless coupling.